Universal joints of the mechanical type are widely used for transmitting torque between a pair of rotating members. But, these universal joints require periodic servicing and maintenance, such as frequent lubrication of the bearings and connections thereof. This is especially vexatious to the truck or automobile owner, since the servicing job takes time and effort. Moreover, in many vehicular applications these joints are almost inaccessible, so that the required periodic maintenance is omitted and the life of the universal joint is greatly reduced.
For the most part, mechanical universal joints permit the transmission of power at larger angles of misalignment than is the case with flexible couplings which utilize a yieldable material in compression. On the other hand, such flexible couplings usually require no lubrication and therefore are particularly useful in locations where access is difficult. Exemplifying the art in this area are U.S. Pat. No. 3,724,239 issued Apr. 3, 1973 to M. M. Calistrat, and an article by Mr. R. R. Grundtner in the Dec. 18, 1969 issue of Machine Design entitled "Couplings." However, although these compression-type flexible couplings advantageously absorb drive line shocks, they suffer several disadvantages. Firstly, they are often relatively complex and costly in construction. Secondly, they are typically limited to only a few degrees of angular misalignment. Thirdly, they sometimes impose undesirable reaction loads on the connecting shaft members and their support bearings, substantially reducing the service life thereof. And fourthly, under heavy loads the elastic cushions tend to fail prematurely from fatigue or by permanent deformation.
Another type of flexible coupling is disclosed in British Patent Specification No. 1,503,110 to Regie Nationale Des Usines Renault, published Mar. 8, 1978. In that reference a grooved intermediate torque transmitting ball member of elastic or plastic material is connected by two wire ring elements individually having a head forming a practically closed circular annulus. The axes of the ring elements are at right angles to each other and are also nonintersecting or offset. However, that construction is undesirable because of the complexities evolving from such offset axes and the reduced contact area between the interlaced ring element heads and the grooves in the ball member. Not only are undesirably low load-carrying and speed capacities anticipated with that coupling, but also the ring elements must be undesirably deformed during introduction of the ball member making that construction more difficult to assemble.
The flexible coupling of the present invention is directed to overcoming one or more of the problems as set forth above.